The invention relates to a marine drive having two counter-rotating surface operating propellers.
The invention arose during development efforts directed toward a marine drive enabling increased top end boat speed. Surfacing drives for eliminating torpedo drag are known in the art, for example U.S. Pat. No. 4,871,334, column 3, lines 35+.
In one aspect of the present invention, the drive housing is provided with a low drag specially contoured surfacing torpedo.
In another aspect, the torpedo portion of the housing has outer surface profiles along horizontal cross-sections defining wedges with sharp leading tips forming a sharp leading edge for slicing through the water at the surface.
In another aspect, the torpedo portion has an upper zone with outer surface profiles along horizontal cross-sections defining wedges with sharp leading tips forming a sharp leading edge for slicing through the water, the sharp leading tips forming a sharp leading edge defining a first line extending downwardly and rearwardly at a given angle relative to vertical. The torpedo portion has a lower zone with outer surface profiles along horizontal cross-sections defining wedges with leading tips defining a second line extending downwardly and rearwardly at a second angle relative to vertical, the second angle being greater than the first angle.
In another aspect, the housing includes a skeg extending downwardly from the lower zone of the torpedo portion, the skeg having a leading edge defining a third line extending downwardly and rearwardly at a third angle relative to vertical, the third angle being greater than the first angle and less than the second angle.